If you get there early and go to the low capacity rides like Fahrenheit first, and follow a good schedule, the lines shouldn't be a problem if you know what you're doing. I usually like to go to Fahrenheit first, and do the rides near the center of the park. Then I like to go to Great Bear, then go to the other rides near the front of the park. Then I wait a while, eat, or take videos or pictures, then go to the back at the park when most of the crowds are at the water park. It also depends on what rides you want to do. If you want to get every coaster credit, you could definitely get it done in one day easily. If you want to go on water rides (Coal Cracker is one of the best log flumes I've been on), or flat rides, it will be a little bit more difficult. But it can still be done in one day. If it's possible, I would recommend getting the Preview Plan. This lets you get into the park 2.5 hours before the park closes on one evening, and then you get the whole day afterwards. This lets you do the rides at the front of the park while most of the crowds are near the back of the park. If you do the Preview Plan, you can do everything done with no problem. I've been going to this park for almost 10 years since I was very small, and this is what has worked for my family the most. This is one of the best parks in the country, and I hope you have a great time!
What about getting a two-day pass? That's what I was planning on doing to make sure I could get everything done plus rerides. I wouldn't be able to preview because I'd be going all day Friday and Saturday anyway, but if I just went on Saturday I could preview on Friday. I'm talking about summer opening weekend, BTW. I have no idea how busy the park might be so I figured I'd feel better if I had two days at the park, but I'm open to other suggestions. If I only did one day, I could probably fit in another theme park that weekend. I'm already planning Knoebel's for Sunday but there are other parks in the area that I've never been to, like Dorney.
My personal advice to you would be to do a two day pass for Hershey and skip Dorney, unless you're crazy about waterparks. Wildwater Kingdom at Dorney blows Hershey's Boardwalk out of the water (pun intended?). Hershey also has so many tourist options in the surrounding areas, like the Hershey Gardens, Chocolate World (duh), and the trolley tour. If you've never been to the area, it's really stunning in the summertime and you would be better off doing the park and some of those activities.
Just my two cents!
And oh yeah. Skyrush. That's all.